Apparatus and method for stepper exposure control in photography

Abstract

An apparatus and a method for stepper exposure control by utilizing a shutter assembly formed of electro-optic crystal materials in a photolithographic process are disclosed. In the apparatus, a series of control panels are stacked together to form a shutter assembly. Each of the control panel is formed by depositing a multiplicity of parallel, spaced-apart lines of electro-optic crystal material on a polarizer sheet. Two of such polarizer sheets are then stacked together with the lines parallel to each other and the lines on the top panel overlapping the spacing on the bottom panel. Two bottom panels are formed similarly however, positioned with the lines perpendicular to the lines in the first and second control panel when assembled together in the shutter assembly. A suitable electro-optic crystal material used should withstand a high temperature environment. One of such suitable material is LiNbO 3 . The control panels can also be formed by embedding the electro-optic crystal material in a polarizer material layer and then depositing a transparent, insulative material such as SiO 2 on top for protection and insulation.

What is claimed is:  
     
       1. An apparatus for controlling light transmission comprising: 
       a first polarizer sheet,  
       a first multiplicity of parallel, spaced-apart lines formed of an electro-optic crystal material on said first polarizer sheet, said lines having a pre-set spacing of “X” thereinbetween,  
       a second polarizer sheet on top of said first multiplicity of parallel, spaced-apart lines,  
       a second multiplicity of parallel, spaced-apart lines formed of an electro-optic crystal material on said second polarizer sheet substantially parallel to and overlapping said spacing “X” of said first multiplicity of lines,  
       a third polarizer sheet on top of said multiplicity of lines,  
       a third multiplicity of parallel, spaced-apart lines formed of an electro-optic material and in a perpendicular direction to said first and second multiplicity of lines on said third polarizer sheet, said third multiplicity of lines having a pre-set spacing of “Y” therebetween,  
       a fourth polarizer sheet on top of said third multiplicity of lines,  
       a fourth multiplicity of parallel, spaced-apart lines formed of an electro-optic material on said fourth polarizer sheet substantially parallel to and overlapping said spacing of “Y” of said third plurality of parallel, spaced-apart lines, and  
       a transparent, electrically insulative material embedding said fourth multiplicity of parallel, spaced-apart lines.  
     
     
       2. An apparatus for controlling light transmission according to claim  1  further comprising a transparent, electrically insulative material embedding each of said first, second and third multiplicity of parallel, spaced-apart lines. 
     
     
       3. An apparatus for controlling light transmission according to claim  2 , wherein said transparent, electrically insulative material comprises SiO 2 . 
     
     
       4. An apparatus for controlling light transmission according to claim  1  further comprising electrical wiring means for providing electrical communication with each of said first, second, third and fourth multiplicity of parallel, spaced-apart lines. 
     
     
       5. An apparatus for controlling light transmission according to claim  1  further comprising electrically wiring means, power supply and logic control unit forming a a grating unit for a stepper. 
     
     
       6. An apparatus for controlling light transmission according to claim  1 , wherein said electro-optic crystal comprises LiNbO 3 . 
     
     
       7. An apparatus for controlling light transmission according to claim  1 , wherein a width of said first and second multiplicity of parallel, spaced-apart lines is larger than said “X” spacing. 
     
     
       8. An apparatus for controlling light transmission according to claim  1 , wherein a width of said first and second multiplicity of parallel, spaced-apart lines is larger than said “X” spacing by at least 10% “X”. 
     
     
       9. An apparatus for controlling light transmission according to claim  1 , wherein a width of said third and fourth multiplicity of parallel, spaced-apart lines is larger than said “Y” spacing. 
     
     
       10. An apparatus for controlling light transmission according to claim  1 , wherein a width of said third and fourth multiplicity of parallel, spaced-apart lines is larger than said “Y” spacing by at least 10% “Y”. 
     
     
       11. An apparatus for controlling light transmission according to claim  1 , wherein a total planar surface area formed by said first multiplicity of parallel, spaced-apart lines is between about 1 mm×1 mm and about 100 mm×100 mm. 
     
     
       12. An apparatus for controlling light transmission according to claim  1 , wherein a width of said first, second, third and fourth multiplicity of parallel, spaced-apart lines is between about 1 μm and about 100 μm. 
     
     
       13. An apparatus for controlling light transmission according to claim  1 , wherein each of said first, second, third and fourth multiplicity of parallel, spaced-apart lines is controlled by an independent logic circuit. 
     
     
       14. An apparatus for controlling light transmission according to claim  1 , wherein said first, second, third and fourth multiplicity of parallel, spaced-apart lines are embedded in a polarizer material layer deposited on a quartz plate. 
     
     
       15. A shutter for exposure control in a stepper used in photolithography comprising: 
       a light transmission control unit formed by a multiplicity of parallel, spaced-apart lines of an electro-optic crystal embedded in a polarizer material layer deposited on a quartz plate, and  
       an exposure control shutter formed by four light transmission control units stacked together in an up-and-down configuration, the top two control units are stacked in such a way that the multiplicity of parallel, spaced-apart lines in a top-most control unit overlaps spacings between said multiplicity of parallel, spaced-apart lines in a second control unit positioned below said topmost control unit, the bottom two control units are stacked in such a manner that said multiplicity of parallel, spaced-apart lines are perpendicular to said multiplicity of parallel, spaced-apart lines in said top two control units, and the multiplicity of parallel, spaced-apart lines in a third control unit overlaps spacings between said multiplicity of parallel, spaced-apart lines in a fourth control unit.  
     
     
       16. A shutter for exposure control in a stepper according to claim  15 , wherein said electro-optic crystal comprises LiNbO 3 . 
     
     
       17. A shutter for exposure control in a stepper according to claim  15 , wherein said multiplicity of parallel, spaced apart lines having a width that is larger than a width of said spacings. 
     
     
       18. A shutter for exposure control in a stepper according to claim  15 , wherein said multiplicity of parallel, spaced-apart lines having a width that is larger than a width of said spacings by at least 10% of said spacing width. 
     
     
       19. A shutter for exposure control in a stepper according to claim  15  further comprising electrical wiring means, power supply means and logic control means. 
     
     
       20. A shutter for exposure control in a stepper according to claim  15 , wherein said multiplicity of parallel, spaced-apart lines each having a width between about 1 mm and about 100 mm. 
     
     
       21. A method for controlling light transmission comprising the steps of: 
       providing a shutter formed by a first polarizer sheet, a first multiplicity of parallel, spaced-apart lines of an electro-optic crystal material on said first polarizer sheet, said lines having a pre-set spacing of “X” thereinbetween, a second polarizer sheet on top of said first multiplicity of parallel, spaced-apart lines, a second multiplicity of parallel, spaced-apart lines formed of an electro-optic crystal material on said second polarizer sheet substantially parallel to and overlapping said spacing “X” of said first multiplicity of lines, a third polarizer sheet on top of said second multiplicity of lines, a third multiplicity of parallel, spaced apart lines formed of an electro-optic material and positioned in a perpendicular direction to said first and second multiplicity of lines on said third polarizer sheet, said third multiplicity of lines having a pre-set spacing of “Y” therebetween, a fourth polarizer sheet on top of said third multiplicity of lines, a fourth multiplicity of parallel, spaced-apart lines formed of an electro-optic material on said fourth polarizer sheet substantially parallel to and overlapping said spacing of “Y” of said third plurality of parallel, spaced-apart lines, and a transparent, electrically insulative material embedding said fourth multiplicity of parallel, spaced-apart lines,  
       electrically connecting said first, second, third and fourth multiplicity of parallel, spaced-apart lines to a power supply and a logic control unit, and  
       inputting electrical power to said first, second, third and fourth multiplicity of parallel, spaced-apart lines for controlling light transmission through said shutter.  
     
     
       22. A method for controlling light transmission according to claim  21  further comprising the step of forming said first, second third and fourth multiplicity of spaced-apart lines in LiNbO 3 .